Commit 9a6e2dcf authored by Xiao Guangrong's avatar Xiao Guangrong Committed by Paolo Bonzini
Browse files

mc146818rtc: update periodic timer only if it is needed 



Currently, the timer is updated whenever RegA or RegB is written
even if the periodic timer related configuration is not changed

This patch optimizes it slightly to make the update happen only
if its period or enable-status is changed, also later patches are
depend on this optimization

Signed-off-by: default avatarXiao Guangrong <xiaoguangrong@tencent.com>
Message-Id: <20170510083259.3900-2-xiaoguangrong@tencent.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 65dfad62

hw/timer/mc146818rtc.c

+16 −2
Original line number Diff line number Diff line
@@ -391,6 +391,7 @@ static void cmos_ioport_write(void *opaque, hwaddr addr, 
                              uint64_t data, unsigned size)

{

    RTCState *s = opaque;

    bool update_periodic_timer;



    if ((addr & 1) == 0) {

        s->cmos_index = data & 0x7f;
@@ -423,6 +424,8 @@ static void cmos_ioport_write(void *opaque, hwaddr addr, 
            }

            break;

        case RTC_REG_A:

            update_periodic_timer = (s->cmos_data[RTC_REG_A] ^ data) & 0x0f;



            if ((data & 0x60) == 0x60) {

                if (rtc_running(s)) {

                    rtc_update_time(s);
@@ -445,10 +448,17 @@ static void cmos_ioport_write(void *opaque, hwaddr addr, 
            /* UIP bit is read only */

            s->cmos_data[RTC_REG_A] = (data & ~REG_A_UIP) |

                (s->cmos_data[RTC_REG_A] & REG_A_UIP);



            if (update_periodic_timer) {

                periodic_timer_update(s, qemu_clock_get_ns(rtc_clock));

            }



            check_update_timer(s);

            break;

        case RTC_REG_B:

            update_periodic_timer = (s->cmos_data[RTC_REG_B] ^ data)

                                       & REG_B_PIE;



            if (data & REG_B_SET) {

                /* update cmos to when the rtc was stopping */

                if (rtc_running(s)) {
@@ -475,7 +485,11 @@ static void cmos_ioport_write(void *opaque, hwaddr addr, 
                qemu_irq_lower(s->irq);

            }

            s->cmos_data[RTC_REG_B] = data;



            if (update_periodic_timer) {

                periodic_timer_update(s, qemu_clock_get_ns(rtc_clock));

            }



            check_update_timer(s);

            break;

        case RTC_REG_C: